Torsion angle force constants

The first four terms represent the bonded interactions that is, bonds, angles, proper torsions and improper torsions. In eq 11.1, kb is the bond force constant, (/ — /q) is the distance from equilibrium bond length that the atom has moved, kg is the angle force constant, (0 0q) is th angle from equilibrium between three... 

I lic 3-alorn and 4-atoni rcstrairiis behave just like those for two atoms, except tliat the dialog hox requests an angle rather than a distance and the accompanying request for a force constant requires either a bending force constant (3-atorn case) or a torsional force con Stan t (4-atorn case). 

You can add restraints to any molecular mechanics calculation (single point, optimization or dynamics). These might be NMR restraints, for example, or any situation where a length, angle, or torsion is known or pre-defined. Restraints with large force constants result in high frequency components in a molecular dynamics calculation and can result in instability under some circumstances. 

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